Technical Field
The present invention relates to a method of measuring perchlorate contamination. More particularly, the present invention relates to a microwave assisted parallel electromembrane extraction method coupled with ion chromatography method to detect and quantify trace levels of perchlorate ions in produce, food and environments with complex background matrices.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Contamination by the ionic perchlorate (ClO4−) has increasingly become a human concern especially in areas surrounding aerospace operations, pyrotechnics and munitions (E. Urbansky, Environ. Sci. Pollut. R. 9 (2002) 187; E. T Urbansky, Biorem. J. 2 (1998) 81; Y. Liu, S. Mou, J. Chromatogr. A 997 (2003) 225; M. L. Magnuson, E. T. Urbansky, C. A. Kelty, Ana. Chem. 72 (2000) 25—each incorporated herein by reference in its entirety). Both aquatic and terrestrial species are prone to perchlorate contamination (P. N. Smith, C. W. Theodorakis, T. A. Anderson, R. J. Kendall, Ecotoxicology 10 (2001) 305; J. E. Canas, Q. Cheng, K. Tian, T. A. Anderson, J. Chromatogr. A 1103 (2006) 102—each incorporated herein by reference in its entirety). Such level of contamination is of profound toxicological interest since perchlorate can potentially interfere with normal thyroid function which leads to hormonal and metabolic disruptions (K. Saito, K. Yamamoto, T. Takai, S. Yoshida, Acta Endocrinologica 104 (1983) 456—each incorporated herein by reference in its entirety). The ion has a highly delocalized anionic charge and a large atomic volume resulting in low anionic charge density which facilitates the extreme solubility of the perchlorate salts in water matrices ((E. Urbansky, Environ. Sci. Pollut. R. 9 (2002) 187; P. N. Smith, Environ. Pollut. 132 (2004) 121; A. B. Kirk, E. E. Smith, K. Tian, T. A. Anderson, P. K. Dasgupta, Environ. Sci. Technol. 37 (2003) 4979—each incorporated herein by reference in its entirety). Evaluating tissue level contamination is paramount in determining significant toxicological and ecological exposure to perchlorate ion (A. B. Kirk, E. E. Smith, K. Tian, T. A. Anderson, P. K. Dasgupta, Environ. Sci. Technol. 37 (2003) 4979—incorporated herein by reference in its entirety). Up to date, suppressed ion chromatography (IC) coupled with conductivity detector has been used to quantify perchlorate to parts-per-billion (ppb) method detection limit (MDL) in water matrix without preconcentration (E. T. Urbansky, B. Gu, M. L. Magnuson, G. M. Brown, C. A. Kelty, J. Sci. Food Agric. 80 (2000) 1798; H. P. Wagner, B. V. Pepich, C. Pohl, D. Later, R. Joyce, K. Srinivasan, D. Thomas, A. Woodruff, B. Deborba, D. J. Munch, J. Chromatogr. A 1118 (2006) 85—each incorporated by reference in its entirety). However, with more complex background matrices, trace detection of perchlorate ion becomes very difficult (H. P. Wagner, B. V. Pepich, C. Pohl, D. Later, R. Joyce, K. Srinivasan, D. Thomas, A. Woodruff, B. Deborba, D. J. Munch, J. Chromatogr. A 1118 (2006) 85; T. W. Collette, T. L. Williams, E. T. Urbansky, M. L. Magnuson, G. N. Hebert, S. H. Strauss, Analyst 128 (2003) 88—each incorporated herein by reference in its entirety). Several clean-up methods that minimize ionic interferences have been suggested (A. B. Kirk, E. E. Smith, K. Tian, T. A. Anderson, P. K. Dasgupta, Environ. Sci. Technol. 37 (2003) 4979; T. A. Anderson, T. H. Wu, Bull. Environ. Contam. Toxicol. 68 (2002) 684; J. J. Ellington, J. J. Evans, J. Chromatogr. A 898 (2000) 193; P. B. Hatzinger, M. C. Whittier, M. D. Arkins, C. W. Bryan, W. J. Guarini, Remed. J. 12 (2002) 69; L. Guo, H. K. Lee, J. Chromatogr. A 1286 (2013) 9; M. Ericsson, A. Colmsjo, J. Chromatogr. A 964 (2002) 11—each incorporated herein by reference in its entirety). Typically, microwave-assisted extraction (MAE) in combination with solid phase extraction (SPE) for sample clean-up has widely been used in preparation of solid samples for instrumental analysis (C. Basheer, J. P. Obbard, H. K. Lee, J. Chromatogr. A 1068 (2005) 221—incorporated herein by reference in its entirety). As an alternative, electromembrane extraction (EME) has recently been used as a single step extraction method and its suitability, fits both charged and ionic compounds (K. F. Seipa, A. Gjelstad, S. Pedersen-Bjergaard, J. Chromatogr. A 1308 (2013) 37—incorporated herein by reference in its entirety). Its mode of operation appears in several scientific publications (C. Basheer, J. Lee, S. Pedersen-Bjergaard, K. E. Rasmussen, H. K. Lee, J. Chromatogr. A 1217 (2010) 6661; K. F. Seip, J. Stigsson, A. Gjelstad, M. Balchen, S. Pedersen-Bjergaard, J. Sep. Sci. 34 (2011) 3410; N. C. Dominguez, A. Gjelstad, A. M. Nadal, H. Jensen, N. J. Petersen, S. H. Hansen, K. E. Rasmussen, S. Pedersen-Bjergaard, J. Chromatogr. A 1248 (2012) 48—each incorporated by reference in its entirety). This method is capable of reducing the extraction time (K. F. Seipa, A. Gjelstada, S. Pedersen-Bjergaard, J. Chromatogr. A 1308 (2013) 37—incorporated herein by reference in its entirety). In most recent publications, EME has demonstrated good sample clean-up, good enrichment, less extraction time as well as low solvent consumption (K. F. Seip, J. Stigsson, A. Gjelstad, M. Balchen, S. Pedersen-Bjergaard, J. Sep. Sci. 34 (2011) 3410; N. C. Dominguez, A. Gjelstad, A. M. Nadal, H. Jensen, N. J. Petersen, S. H. Hansen, K. E. Rasmussen, S. Pedersen-Bjergaard, J. Chromatogr. A 1248 (2012) 48—each incorporated by reference in its entirety). Being a three-phase system, its analytes are preconcentrated in an aqueous acceptor phase giving the resultant extract an edge of direct compatibility with ion chromatography.
Accordingly, the objective of the present invention is to provide methods of quantifying perchlorate contamination in complex environmental matrices wherein detection limits are improved and co-elution of interfering ions present in sample extracts is minimized. A parallel EME mode used has advantages over single EME set-up since multiple samples are extracted simultaneously and this enhances the methods precision and shortens the time for parallel experiments (S. Jian-Nan, C. Juan, S. Yan-Ping, J. Chromatogr. A 1352 (2014) 1—incorporated by reference in its entirety).